71,000 Words
This series began with the devastating effects One Son had on Mulder and Scully's partnership, and continued through their desperate attempt to understand the alien threat and the complex loyalties of Diana and other players. Parts 3 and 4 take place after Biogenesis as Scully and Mulder try to come to terms with his mysterious illness. There's a shippy end for believers...
I've been having a bit of a post One Son indulgence lately so there may be some more juicy One Son fics coming...
In this one Zuffy weaves an elaborate mytharc story around the canon from Two Fathers/One Son to Amor Fati, and challenges our beloved heroes to save each other, not knowing who they can trust.